Location services for determining a user's relative location have become ubiquitous. For example, Global Navigation Satellite Systems such as Global Position System (GPS) provide location services in outdoor environments. For indoor environments, there are many products based on different technologies that provide real-time location services. Applications often have very different requirements for accuracy, real-time latency and etc. At the same time, different technologies generally offer different quality of location service. Providing location services to smart phones and tablet devices has been a focus because of their popularity and ability to integrate with other services.
Using Bluetooth or WiFi signal to estimate location has been implemented because the availability of these devices in consumer products. In one example, iBeacon is an indoor proximity system that Apple Inc. calls “a new class of low-powered, low-cost transmitters that can notify nearby iOS 7 devices of their presence.” The technology enables a device or other hardware to send push notifications to devices in close proximity to the iBeacon devices. Devices can also receive iBeacon advertisements. The iBeacon works on Bluetooth Low Energy (BLE), also known as Bluetooth Smart. BLE can also be found in Bluetooth 4.0 devices that support dual mode. One potential application of iBeacon is a location-aware, context-aware, pervasive small wireless sensor beacon that could pinpoint users' location in a store. iBeacon devices could send notifications of items nearby that are on sale or items customers may be looking for, and it could enable payments at the point of sale (POS) where customers don't need to remove their wallets or cards to make payments. Similar to iBeacon, there are other technologies including RFID and Near Field Communication (NFC) systems that offer ‘proximity sensing’ based location services. Generally, any wireless transmitter with a known location can serve as a beacon device, or beacon.
In another example, there are many commercial systems that utilize WiFi access points (APs) as beacons. WiFi access points are used to determine the location of a WiFi enabled devices. Companies such as Ekahau offer dedicated WiFi-based real-time location system (RTLS) solutions for hospitals, shopping malls, and etc. Many chip companies including Qualcomm (Atheros) and Broadcom offer radio chips with location service support. A WiFi receiver's location can be estimated based on the received signal strength from these APs.
FIG. 1 illustrates an iBeacon proximity sensing system 100, consisting of iBeacon transmitters 101 and receivers 110. The iBeacon transmitter 101, having a known location 103, broadcasts beacon messages 111 which are received by receiver 110. A receiving device 110 can estimate its distance 102 to an iBeacon transmitter 101 using the received signals 111 to determine the receiving device's 110 location 105.
A beacon message typically includes specific information. For example, an iBeacon capable beacon message includes a universally unique identifier, which is picked up by a compatible app or operating system that can be turned into a physical location or trigger an action on the device such as a check-in on social media or a push notification. The location of the beacon transmitter PTX 103 is configured beforehand. Note that in real implementation, most of the beacon devices have both a transmitter and a receiver and are referred to as beacon transceivers 120 (not shown in FIG. 1).
Existing beacon systems require a user to manually enter the locations of the transmitter 103. This is time-consuming and prone to human error. Additionally, the location information is static and not able to be updated in real-time. Therefore, outdated information can cause problems when a beacon is moved or is moving. The system is not able to detect the location change and therefore cannot update the locations of the beacons automatically.
Proximity-sensing systems, like iBeacons, generally offer low power, low cost, and low complexity location services at the price of poor accuracy, large latency and discontinuous (intermittent) services. These systems are not capable of estimating the accurate, up-to-date location of the mobile device. The aforementioned wireless location systems are based on received signal strength and generally have accuracy and resolution measured in meters, or tens of meters. For example, the iBeacon system is only able to detect if a receiver is relatively ‘immediate’, ‘near’, ‘far’, or ‘unknown’. The accuracy afforded by these types of systems is not good enough for certain applications.
In contrast, there are high precision RTLS products available based on other technologies such as Ultra-Wideband (UWB). An UWB RTLS system is capable of providing an accurate location estimate to within 15 cm and has an update rate much higher than 1 Hz. These systems can detect and update the tag locations in real time.
FIG. 2 shows an example of a UWB-based locationing system 200. Typically, an UWB RTLS system consists of an infrastructure network 222 and tags 202. An infrastructure network 222 further consists of multiple UWB anchor devices 201. The tag 202 locations are estimated by measuring the time-of-flight of signals between nodes, or anchor devices 201, which are subsequently converted into distances 210. The anchor device 201 locations are generally known and considered static. However, there are cases when anchor positions can be estimated on the fly. A tag 202 is a device which location is to be determined. The locations of UWB tags 202 can be determined based on the timing information and/or anchor locations provided by the infrastructure network 222. UWB tag 202 locations can be estimated with high accuracy. The location of the tag 202 may be determined by the tag (locally) or by the system (in the back end). A tag being able to determine its own location is referred to as the locationing device hereinafter.
UWB RTLS infrastructure networks can also be designed to be self-locating and self-calibrating. Self-localization refers to the capability of a system determining the anchor locations automatically or semi-automatically. Self-calibration refers to the capability of system detecting, correcting or compensating and changes of anchor position or link condition and correcting the changes if necessary.
While UWB location systems have superior performance in both accuracy and real-time operation, they are not ubiquitously available. Moreover, the cost of UWB transceivers is generally higher, and UWB transceivers are not embedded in most of consumer electronics, such as smart phones and tablets. To take advantage of the location services provided by an UWB RTLS network, a user is required to carry the UWB radio node (UWB tag) as an extra device.
However, there exist many applications in which it is desirable for a number of different use cases to coexist in the same coverage area. Each use case has different Quality of Service (QoS) requirements and constraints such as cost and power. For example, asset tracking and navigation may be both needed for construction site RTLS systems. However, for asset tracking, it is desirable for the tags to be in compact form factor and of low cost. Whereas, for navigation, the accuracy requirements are high. It is therefore desirable to have a unified system that provides different services as opposed to a plurality of separate systems.